Method for expanding perlite



Oct. 23, 1951 E. o. HowLE METHOD FOR EXPANDING PERLITE original Filedsept 17, 1'947 Patented Oct. 23, 1951 UNITED STATES PATENT OFFICE METHODFOR EXPANDING PERLITE Ernest 0. Howie, Chicago, Ill.

Original application September 17, 1947, Serialk No. 774,614. Dividedand this application July 16, 1948, Serial No. 39,048

Claims. l

` 'I'his invention relates to the expansion o f perlite, and amongvother objects, aims to provide a method of and means for more emcicntlyexpanding perlite.

Another object of the invention is to increase the yield of expandedperlite.

Another object is to minimize over-heating of the perlite by removing itfrom the zone of expanding temperatures as soon as it has expanded.

A further object is to effect separation between the expanded perliteand unexpandable and unexpanded materials.

The nature of the invention and other objects and advantages thereofwill readily appear by reference to one illustrative method andapparatus embodying the invention and described in the followingspecification and illustrated in the accompanying drawing.

In said drawing:

Fig. 1 is a sectional elevation of an expanding furnace; and

Fig. 2 is a section, on a larger scale, taken on the plane 2 2 of Figure1, of a burner nozzle of the flame retention type.

This application is a division of co-pending application Serial No.774,614, filed September 17, 1947, which in turn is a Continuation inpart of. application Serial No. 684,452, filed July 18, 1946, nowabandoned. This application covers the generic features of the methodand apparatus for expanding perlite also disclosed and originallyclaimed in said co-pending applications.

f Perlite is a siliceous material of volcanic origin and rhyolitic incomposition. It contains about 2 to 5% of combined Water. When quicklyheated to its softening temperature range the steam formed puffs thematerial to many times its original size to produce a material of verylow bulk density, e. g., 2 to 14 pounds per cubic foot, depending on thedegree and eiciency of expansion. For convenience, the term perlite ishere used in a generic sense to include all expandable volcanic glasses.Perlite diifers considerably, depending on the locality where found, inthe time required for expansion, and in its softening range. Thesoftening range is generally somewhere between 1600 degrees F. to 2600degrees F. A relatively wide softening range is desirable to permit moreefllcient and better control of, expansion. It is diicult to prevent thematerial in its softened condition from cohering or agglomerating andfrom adhering to the walls of the expanding'furnace, with the resulttha-Lu much material is wasted and frequently removal of the layer ofglass from the walls of the furnace is necessary. In this respect,

among others, perlite presents serious problems not encountered in thetreatment of other materials. Even with the most careful grading (whichgreatly increases the cost) it is not possible to obtain material ofsufficiently uniform grain size to respond alike to expandingtemperatures. If the larger grains be expanded properly, the smallergrains will be excessively softened, losing their porosity and adheringto other granules and to the walls of the furnace.

According to my invention, granules of various sizes may besimultaneously expanded without pregrading; and a given granule isexposed to expanding temperatures only long enough to expand it. In itssoftened condition while expanding it is relatively free and unburdenedby substantial contact or weight of other granules or the chamber wallswhich would tend to collapse the expanded particles partly or entirely,thereby reducing their bulk density. When expanded, and as a consequenceof such expansion, it is automatically removed from the expanding zone.The heavier or larger particles remain in the expanding zone a longertime. I utilize the large particle bulk (i. e., lower bulk density)resulting when the granule expands to carry the particle out of theexpanding zone, by subjecting the granules to an upward current of gasesof such velocity as to be capable of carrying the particles away in thegas stream when adequately expanded. Until a granule expands, it remainsin the highly heated expanding zone, its bulk being insufficient to belevitated by force of the gas stream. Rock impurities which do notexpand, eventually fall below the heated zone and may be removed fromtime to time. Such impurities are thus automatically separated from theperlite.

The illustrative furnace is characterized by a generally vertical,elongated cylindrical chamber I0 open at the upper and lower ends andsurrounded by refractory Walls Il. The chamber I0 is heated preferablyby liquid or gaseous fuel ini-reduced through the opening I2 at thebottom of the chamber. The gases of combustion in highly heatedcondition travel upwardly at such velocity that the upward force thereofis sufficient to levitate or carry upward the perlite which has expandedand thereby reduced its bulk density. The force is not sucient to carryup unexpanded or insuiiiciently expanded material.

Thus, the larger granules of ore which take longer to heat remain in theexpanding zone for an appropriate length of time, yet the finer materialwhich is more readily heated is removed as soon as it expands. Rock orother unexpandable or unexpanded impurities eventually fallsdown throughthe narrow annular opening between the walls of the furnace and theburner nozzle I3. The latter preferably has a reduced portion I4 throughwhich the gases.

travel at such high velocity that the material cannot fall into thenozzle even in its relatively heavy condition as unexpanded ore.

As the gases burn and are thereby heated they expand very substantially,and though the-section of the chamber is larger than that of the nozzlei3, the gas velocity nevertheless has sufcient force to levitate thegranules as they expand. At a velocity of about 1100 feet per minute thehot gases exert enough force to levitate expanded granules whose bulkdensity is about 8 pounds per cubic foot.

TheA fuel supply is preferably provided with means,` the details ofwhich form no part of this invention and are readily obtainable on themarket, for adjusting the rate of fuel feed, thereby to vary thevelocity of hot gases through the chamber. One appropriate fuel supplyand regulating means is disclosed in said co-pending application SerialNo. 774,614.

The high temperature zone of the furnace extends well below the point I5at which the granules of perlite ore to be expanded, are introduced. Thepoint I5 is high enough in the chamber to insure heating of the granulesto expanding temperatures as they fall; but as soon as the bulk densityis reduced by expansion their travelV is reversed and they are carriedup and out of the top of the furnace.

Any appropriate means I6 fork feeding the raw ore into the chamber maybe employed. Preferably the granules are introduced into the expandingchamber in a diverging stream so that on entering the chamber theyscatter across its entire section. The feeding means is advantageouslyprovided with some device for adjusting the rate of feed. The details ofthe feeding mechanism form no part of the present invention. The feedingmechanism here illustrated is described in detail in said co-pendingapplication Serial No. 774,614.

As here shown the hot gases carry the expanded granules out of the topof the chamber where they are deflected by the shield I'I into acollecting bin I8.

The expanding chamber is advantageously lined with a refractory metalliner I9, flexibly supported from the upper portion of the chamber andhanging freely therein and spaced from the refractory walls of thechamber. Periodic vibration or jarring of the liner serves to dislodgeany material adhering thereto. The liner may advantageously be made ofstainless steel to withstand the high temperatures in the expandingchamber. Such liner and the mechanism for jarring or vibrating it aredisclosed in detail and claimed in said co-pending application SerialNo. 774,614. A pyrometer 2liv in contact with the outer surface of theliner in the region of the expanding zone serves to indicate approximatetemperatures in the expanding zone.

In an expanding furnace like that here illustrated having an internaldiameter of 18 inches, 2000 cubic feet of natural gas per hour mixedwith 1800 cubic feet of air will create a temperature during expandingoperations, of about 1700 degrees F., on the outside of liner I8 about 3feet above the point where combustion starts. The temperature of thegases is of course substantially above the latter temperature (beingabout 3000 degreesFJ, but the eiective temperature, that is thetemperature to which the granules of perlite are heated, is about 1700to 1900 degrees F. At their combustion temperature, the gases expand tosuch volume that the velocity of the gases up the furnace is about 1100feet per minute. This is suicient to provide the force necessary tolevitate perlite granules having a maximum bulk densiy of about 8 poundsper cubic foot,land thereby to carry them out of the furnace as whenthey expand.

It willbe understood that the specific ore feeding means I6, fuel supplymeans 2|, and gas nozzleI I3, illustrated in the drawing, are thosedisclosed and claimed in said co-pending application Serial No. 774,614,and that their details form no part of the present invention.

Obviously the invention is not limited tov the details of theillustrative method and appara.- tus, since these may be variouslymodified. Moreover, it isnot indispensable that all features of theinvention be used conjointly since various features may be used toadvantage in different combinations and sub-combinations.

Having described my invention, I claim:

1.1The method of expanding intumescing mineral materials which comprisesdirecting upwardly through an elongated chamber open atl its upper andlower endsra stream of hotgases having a high temperature expanding zoneata temperature above that at which the materials intumesce, adjustingthe velocity of said gases at and above said high temperature Zone to avalue which will levitate the material in intumesced condition and.carry `it out of the chamber with the gases but will not levitate thematerial until it has intumesced, feeding a stream of said materialingranular form into said chamber so that it falls downwardly into thehigh temperature zone of said gases and is heated thereby until it isintumesced and levitated by the upward force of said rising hot gases,.and separating the intumesced material from the hot gases after it iscarried thereby from said chamber.

2. The method'of'expanding perlite which comprises directing upwardlythrough an elongated chamber a stream of hot gases having ahightemperature expanding zone at a temperature. above that at which theperlite intumesces, adjusting the velocity of said gases at and abovesaid high temperature zone to a value which will levitate the perlitewhen it has expanded and Will carry it out of the chamber with saidgases but will not levitate the material until it has expanded,feedingperlite of Varying grain sizes into the high temperature zone ofsaid gasesfrom above saidzone to heat the perlite as itfalls, said gasesheating said perlite to expanding temperatures as it thus falls andthereby causing the same to expand and being adapted to carry upwardlythe particles of perlite as and when they expand to low bulk density,unexpandable material falling downwardly out of the lower end of saidchamber,

high temperature expanding zone at a temperature above that at which theperlite will expand, feeding granules of perlite into said stream ofgases at a point substantially above their origin so that said granulesfall downwardly in said stream and are quickly heated thereby duringsaid fall, adjusting the velocity of said gases so that when saidgranules have expanded substantially to reduce their bulk density theywill be levitated by said gases and carried upwardly thereby out of saidchamber, and separating the expanded perlite from the hot gases afterthey issue from said chamber.

4. The method of expanding perlite ore in granular condition whichcomprises directing upwardly through an elongated chamber open at upperand lower ends a stream of hot gases having a high temperature expandingzone in the lower portion of the chamber at a temperature above that atwhich the perlite granules will expand, adjusting the velocity of saidgases at and above said high temperature zone to a value which willlevitate the perlite when it has expanded and will carry it out of thechamber with said gases but will not levitate the material until it hasexpanded, feeding perlite granules into said chamber and allowing thesame to fall freely by gravity into said high temperature zone to heatthe granules to soften and expand same to a bulk density low enough tobe levitated by the upward force of said stream of hot gases, carryingthe softened expanded granules upwardly with said stream of hot gases inrelatively separated condition until said granules have hardenedsufficiently to sustain themselves in expanded condition, the upwardforce of said gases being incapable of levitating unexpanded materialwhich eventually falls out of the lower end of said chamber, and thencarrying the expanded material from the upper portion of said chamberand separating the same from the hot gases.

5. The method of expanding perlite ore in granular condition whichcomprises directing u pwardly through an elongated chamber open at itsupper end a stream of hot gases having a high temperature expanding zonein the lower portion of the chamber at a temperature substantially abovethat at which perlite granules will expand, adjusting the velocity ofsaid gases at and above said high temperature zone to a value which willlevitate the perlite when it has expanded and will carry it out of thechamber with said gases but will not levitate the material until it hasexpanded, feeding perlite granules into said chamber Iand allowing thesame to fall freely by gravity into said high temperature zone inrelatively separated condition to be heated in said high temperaturezone to soft condition and to be expanded to a bulk density low enoughto be levitated by the upward force of said stream of hot gases, wherebythe softened expanded granules are carried upwardly with said stream ofhot gases in relatively separated condition until said granules havehardened suiciently to sustain themselves in expanded condition, saidadjustment of the upward force of said gases being such as to beincapable oi' levitating the unexpanded material, and whereby saidexpanded granules are carried from the upper portion oi the chamber forsubsequent separation from said hot gases.

ERNEST O. HOWLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 821,996 Ellis May 29, 1906920,333 Hughes May 4, 1909 2,112,643 Baensch et al Mar. 29, 19382,119,790 McGehee et al. June 7, 1938 2,334,578 Potters Nov. 16, 19432,421,902 Neushotz ,.k-...,... June 10, 1947

1. THE METHOD OF EXPANDING INTUMESCING MINERAL MATERIALS WHICH COMPRISESDIRECTING UPWARDLY THROUGH AN ELONGATED CHAMBER OPEN AT ITS UPPER ANDLOWER ENDS A STREAM OF HOT GASES HAVING A HIGH TEMPERATURE EXPANDINGZONE AT A TEMPERATURE ABOVE THAT AT WHICH THE MATERIALS INTUMESCE,ADJUSTING THE VELOCITY OF SAID GASES AT AND ABOVE SAID HIGH TEMPERATUREZONE TO A VALUE WHICH WILL LEVITATE THE MATERIAL IN INTUMESCED CONDITIONAND CARRY IT OUT OF THE CHAMBER WITH THE GASES BUT WILL NOT LEVITATE THEMATERIAL UNTIL IT HAS INTUMESCED, FEEDING A STREAM OF SAID MATERIAL INGRANULAR FORM INTO SAID CHAMBER SO THAT IT FALLS DOWNWARDLY INTO THEHIGH TEMPERATURE ZONE OF SAID GASES AND IS HEATED THEREBY UNTIL IT ISINTUMESCED AND LEVITATED BY THE UPWARD FORCE OF